Standard Model predictions for B → Kℓ+ℓ−, B → Kℓ−1ℓ+2 and B → Kv¯v using form factors from Nf = 2 + 1 + 1 lattice QCD

Parrott, W.G., Bouchard, C. and Davies, C.T.H. (2023) Standard Model predictions for B → Kℓ+ℓ−, B → Kℓ−1ℓ+2 and B → Kv¯v using form factors from Nf = 2 + 1 + 1 lattice QCD. Physical Review D, 107(1), 014511. (doi: 10.1103/PhysRevD.107.014511)

Abstract

We use HPQCD’s recent lattice QCD determination of B → K scalar, vector and tensor form factors to determine Standard Model differential branching fractions for B → K ℓ + ℓ − , B → K ℓ + 1 ℓ − 2 and B → K ν ¯ ν . These form factors are calculated across the full q 2 range of the decay and have smaller uncertainties than previous work, particularly at low q 2 . For B → K ℓ + ℓ − we find the Standard Model branching fraction in the q 2 region below the squared J / ψ mass to exceed the LHCb results, with tensions as high as 4.7 σ for B + → K + μ + μ − . For the high q 2 region we see 3 σ tensions. The tensions are much reduced by applying shifts to Wilson coefficients C 9 and C 10 in the effective weak Hamiltonian, moving them away from their Standard Model values consistent with those indicated by other B phenomenology. We also update results for lepton-flavor ratios R μ e and R τ μ and the “flat term,” F ℓ H in the differential branching fraction for ℓ ∈ { e , μ , τ } . Our results for the form-factor dependent contributions needed for searches for lepton-flavor violating decays B → K ℓ − 1 ℓ + 2 achieve uncertainties of 7%. We also compute the branching fraction B ( B → K ν ¯ ν ) with an uncertainty below 10%, for comparison with future experimental results.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Parrott, Mr William and Davies, Professor Christine and Bouchard, Dr Chris
• Authors: Parrott, W.G., Bouchard, C., and Davies, C.T.H.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Physical Review D
• Publisher: American Physical Society
• ISSN: 2470-0010
• ISSN (Online): 2470-0029
• Published Online: 24 January 2023
• Copyright Holders: Copyright © 2023 American Physical Society
• First Published: First published in Physical Review D 107(1): 014511
• Publisher Policy: Reproduced under a Creative Commons License

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
306883		Research in Particle Physics Theory - Phenomenology from lattice QCD and collider physics	Christine Davies	Science and Technology Facilities Council (STFC)	ST/T000945/1	P&S - Physics & Astronomy